Utilities are switching off older coal and gas power plants. Are they adding low- and zero-carbon replacements at a fast enough rate?
Energy Blog: Will Power Plant Retirements Green the Grid?
Jan 20, 2022
by Jeffrey Winters
Electric vehicles have some wonderful attributes, especially in terms of parts count and maintenance, but they won’t cut carbon emissions unless the grid they draw electricity from is low- or zero-carbon. (That’s the case in Norway, where 97 percent of the electricity generated there comes from wind and hydropower.) In the United States, where the electric generation system is still dominated by coal and natural gas, EVs need to be paired with a cleaner grid.
As I wrote in the June/July 2021 cover story for Mechanical Engineering magazine, “greening” the grid can come from two directions, adding new zero-carbon electricity sources or retiring coal- and gas-fired power plants. Emily Grubert, an engineering professor at Georgia Tech in Atlanta, has observed that if existing coal and gas generating assets retire at their expected end of life, those retirements would eliminate some three-quarters of power sector carbon emissions by 2035. The rest would age out in the decade following.
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That observation prompts two major questions. The first is, are coal (and to a lesser extent gas) plants retiring at the necessary pace? According to the Energy Information Agency, some 15 GW of generating assets are scheduled to be retired in 2022. That includes 12.6 GW of coal capacity accounting for 6 percent of the coal fleet operating at the end of 2021. Carrying the rate of retirements to 2035 would eliminate about 75 percent of the existing coal fleet. So far, on target. Gas-powered generation looks to be holding on more firmly than the aging of the fleet would suggest, with only 1.2 GW of retirements scheduled in 2022.
With most things, building capacity is much harder than eliminating it, and that’s true especially with electric power infrastructure, which can be hard to site close to cities and towns where the power is needed. According (again) to the EIA, additions to the electric power system are expected to be robust in 2022, with 46.1 GW of new utility-scale electric generating capacity having been announced. Nearly 80 percent of that new nameplate capacity is zero-carbon, and the rest is fueled by natural gas, which has a much smaller carbon impact than the coal power it is replacing.
The nameplate capacity can be misleading. 21.5 GW of solar power sounds like it should more than make up for the power plant retirements, but the capacity factor—the average amount of net electricity produced compared to its nameplate capacity—for solar ranged by month in 2021 from 16.2 percent to 31.9 percent, according to the EIA—and obviously solar produces no power at night. So realistically, the added solar is equivalent to around 5 GW.
More on Climate Action: Process Heat without CarbonWind’s capacity factor is around 33.3 percent, so the 7.6 GW of nameplate capacity to be added this year—including nearly 1 GW from the Traverse Wind Energy Center in Oklahoma—is the equivalent of about 2.5 GW. And the EIA counts 5 GW of battery storage as part of the additions to generating capacity, but that power is only as clean as the sources that charge the batteries.
Nuclear power runs at close to full capacity and operates emissions-free, so the two reactors at the Vogtle nuclear power plant in Georgia should contribute close to their combined 2.2 GW of power when they come online this year.
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When capacity factors are accounted for, the actual zero-carbon power additions to the grid this year will be about the same as those from gas-fired plants. Retirements are important for reducing carbon from the U.S. electric grid, but if renewables and nuclear can’t add power faster than new natural gas, then the goal of a zero-carbon electric sector will be impossible to reach.
Jeffrey Winters is editor in chief of Mechanical Engineering magazine.